Cellular Differentiation, Stem Cells & Modern Medicine Flashcards

1
Q

Describe how cells become more specialises and less flexible during development

A
  • An embryo begins as a small number of naive, totipotent cells
  • Embryonic stem cells can give rise to all cell types except trophectoderm (pluripotent)
  • A cell’s fate is progressively limited until it becomes terminally differentiated and can only give rise to the same type of cell

Development process is: 8-cell stage to cell polarisation, to compaction, to inner, apolar cells cut off, to trophectoderm fully formed (formally polar) and embryo (in the middle).

Exception: stem cells, germ cells (eggs and sperm)

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2
Q

Describe the three steps a cell takes to get from an embryonic precursor cell to different parts of a muscle fibre?

A
  1. embryonic cells are not differentiated (embryonic precursor cell)
    - At this stage in development the cell could become any type of differentiated cell
    - Muscle specific genes are not being transcribed
  2. Then their fate becomes determined (myoblast - determined)
    - The cell must now develop into a muscle cell
    - Certain control genes which code for transcription factors become activated
    (MyoD protein is a transcription factor)
  3. Finally, the cell is terminally differentiated, playing a functional role in the organism (part of a muscle fibre - fully differentiated cell)
    - A different transcription factor binds to the genes in different places and other proteins are formed (that help the cell do its particular functions)
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3
Q

What is genomic equivalence?

A

Differentiated cells contain all the DNA required to build an entire new organism

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4
Q

What did John B. Gurdon and Shinya Yamanaka do?

A

Took a frog embryo and a nucleus from one of them, and transferred it into an empty egg (an egg that had been radiated by UV light so it was sterile)

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5
Q

Describe how Embryonic Stem Cells are harvested and what they do

A
  • These are ‘harvested’ from the inner cell mass (future embryo) of mammalian blastocyst embryos.
  • Human embryonic stem cells are pluripotent: they can develop into any of the 200 or so types of cell in our bodies given the right conditions
  • The cells derived from these ESCs are genetically indentical to the embryo donor
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6
Q

Describe Induced Pluripotent Stem (iPS) Cells

A
  • iPS cells are made by reprogramming adult skin cells
  • iPS cells can be made from anyone, and are genetically identical to the source skin cells. As they are also pluripotent, they can generate any cell type
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7
Q

Describe Adult (Tissue) Stem Cells

A
  • Stem cells can divide without limit
  • They are undifferentiated, multipotent cells
  • They can divide and give rise to both stem cells and cells which will go on to differentiate into one or more (but not all) types of functional tissue cells
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8
Q

Describe Umbilical Cord Stem Cells

A
  • Cord blood banking is now common practice in some countries
  • Stem cells from blood isolated from he umbilical cord of newborn babies are kept frozen (banked)
  • The stem cells are multipotent, as they are immature blood stem cells. They are less restricted than blood stem cells from adults
  • Can be used to treat leukaemia and many other blood diseases
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9
Q

Describe the renewal tissues in Adult Stem Cells

A
  • Stem cells are important for tissues such as blood and skin which need constant renewing
  • Blood stem cells or haematopoietic stem cells are found in the bone marrow and can be used for transplants
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10
Q

Describe the differences between Adult and Embryonic Stem Cells

A

Embryonic Stem Cells:
- A fertilised egg is totipotent, able to give rise to all cell types via cell division
- Embryonic stem cells are pluripotent, and can become all/any cells of the body

Adult Stem Cells:
- Adult Stem cells such as bone marrow cells usually only give rise to one or a few cell types: multipotent

Different culture conditions are used to persuade stem cells to develop into different kinds of differentiated cells

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11
Q

What is the importance of Stem Cells in Modern Medicine?

A
  • Integrative gene therapy is based on the idea that it may be possible to alter the genetic code of an individual’s cells
  • It is proposed as a way of correcting single gene disorders
  • A normal allele could be inserted into the cells of the affected tissue
  • A virus can deliver genetic material into human cells
  • CRISPR editing may also be used
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12
Q

What is the importance of Stem cells in Modern Medicine in terms of regenerative medicine?

A
  • Regenerative medicine is based on the idea that pluripotent stem cells can be used to repair or replace damaged organs or tissues
  • Pluripotent stem cells can be made from skin cells or blood cells from a patient (genetically identical) or matched donors, or from embryos
  • These stem cells can be encouraged to differentiate into specific cell types such as neurons, or retinal cells
  • The different cells can be transplanted into patients
  • Example: iPSC-derived corneal transplants
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13
Q

Totipotent, vs Pluripotent, vs Multipotent

A

Totipotent:
- able to give rise to all cell types via cell division
- has the potential to divide until it creates an entire, complete organism

Pluripotent:
- able to give rise to most/all cells of the body
- canNOT develop into a complete organism on its own

Multipotent:
- able to give rise to only one or a few cell types

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